We sort kids into the smart and non-smart labels when they are young, and those labels tend to stick, even when what we're measuring isn't raw intelligence but just variance in childhood development that wash out in the long term. I don't think either group is well served by this.

A smart kid can be anything from not eating rocks anymore to multiplying numbers at an early age.

Most of us turn out like the rescued exotic bird which turns out to be a seagull covered in curry.